In Japan, when installing latent Heat Condensing Boilers in multi-family housing, it is currently common to install them outside of open hallways but the exhaust gas temperature is low and the risk of residual gas accumulating due to a decrease in natural ventilation capacity is increasing. In order to collect data to inform setting of policy for equipment installation standards related to positioning of the air supply inlets during normal ventilation when installed in open corridors, experiments using full-size models and investigations using CFD were conducted. It was confirmed that use of a reducer to improve the exhaust resulted in an improvement in accumulation of exhaust gases in corridors, and the concentration of gases was lowered at the air supply inlet. Further, air supply inlet concentrations change according to the relationships between the heights of the ceiling, handrails, and heat source devices; corridor width also has an effect.